[B:<X>,<Y>, <W>,<H>, <Color>]
[B:<X1>,<Y1>,<W1>,,<Color>,<X2>,<Y2>,<W2>,
]
[B:<X1>,<Y1>,<W1>, ,<Color>, <X2>,<Y2>,<W2>,
, <X3>,<Y3>,<W3>,
, ...
]
A rectangular field is filled with the colour <Color>.
If <Color> is missing, the field will be filled with the colour of its upper left corner.
Mismatched parenthesys